Overview
- Shahidi, S. et al. (1993) Biochim. Biophys. Acta 1157, 74.
Alomone Labs Apamin-Biotin blocks rat SK2 channels stably transfected in HEK293T cells.A. Time course of Apamin-Biotin (#STA-200-B) action on SK2 channels. Current amplitudes were plotted as a function of time. Membrane potential was held at -80 mV and cells were stimulated by a 150 ms voltage ramp from -120 mV to +60 mV every 10 sec. 1 nM, 10 nM and 50 nM Apamin-Biotin were perfused during 120 sec as indicated by the bar at 0 mV. B. Superimposed examples of SK2 channel current in the absence (control, black) and presence of 1 nM (green), 10 nM (red) and 50 nM (blue) Apamin-Biotin (taken from the experiment in A).
Alomone Labs Apamin-Biotin stains rat parietal cortex.Lightly-fixed sections of rat brain were incubated overnight with Apamin-Biotin (#STA-200-B) (1 nM) followed by 45 minutes fixation in cold 4% paraformaldehyde and followed by the addition of streptavidin labeled with ATTO-594. Most of the staining is seen in pyramidal neurons (horizontal arrows) as well as in astrocyte-like processes (vertical arrows).
Apamin is a natural peptide isolated and purified from Apis mellifera bee venom. Apamin blocks small conductance Ca2+-activated K+ channels (SK). It is specific for the SK1-3 isoforms, but ineffective in blocking other calcium activated K+ channels2. In mammalian cell lines, Apamin blocks expressed hSK1 with an IC50 of ~10 nM3, rSK1 and rSK2 with IC50 of ~3 and <1 nM respectively4 and liver rSK3 with IC50<1 nM.5 In Jurkat T-cells, 5 nM of Apamin blocks 70% of hSK2 currents.6
Blocking these channels with Apamin slows down neuronal activity after hyperpolarization7, as well as smooth muscle contraction8 and catecholamine secretion in adrenal glands.9 Electrophysiology application of long (~400 ms) voltage ramps, covering the whole physiological range (-160 to +40 mV), in the whole cell patch-clamp or voltage clamp configurations, before and after bath perfusion of the drug, allows the detection of the blocked channel currents (by comparison).1
